Posted
by
kdawson
on Friday March 12, 2010 @12:10PM
from the just-one-word-young-man dept.

arcticstoat calls our attention to MIT research that has produced a version of polyethylene that can conduct heat away from computer chips. Polyethylene is the most widely used plastic. It's not clear how practical this research is for industrial-scale use, involving as it does an atomic-force microscope. The work is detailed in a paper published in Nature Nanotechnology this month. "The new process causes the polymer to conduct heat very efficiently in just one direction, unlike metals, which conduct equally well in all directions. ... The key to the transformation was getting all the polymer molecules to line up the same way, rather than forming a chaotic tangled mass, as they normally do. The team did that by slowly drawing a polyethylene fiber out of a solution, using the finely controllable cantilever of an atomic-force microscope, which they also used to measure the properties of the resulting fiber. This fiber was about 300 times more thermally conductive than normal polyethylene along the direction of the individual fibers, says the team’s leader..."

Sounds like NewEgg accidentally shipped some top-secret prototype chips which us plebs didn't even know how to use. I suppose that was why they made them appear to be plastic toys, so that we'd never figure out how to interface to them. In reality, they have advanced plastic heat sinks (electrical insulators), and even more advanced plastic processors. There's a knock at the door, one mome

Hasnt anyone considered that those "fakes" are actually highly advanced technology from the future that the International Time Police Force wasnt able to stop from leaking into the past?

Think of it this way. If an 18th century intellectual found a microchip, he'd think it a just a weird little black rock. We just think those fakes are a weird little bit of plastic. Now we wait for the futuristic motherboard that will run them. I'll be going through the dumpster behind work in about an hour looking for them

Generally, plastic is not electrically conductive. Which makes it good for mounting electronics. But it is also not heat conductive. Which makes it near worthless for mounting.
A non-electric conductive, but heat conductive material would be very useful. Especially if it is CHEAP. It could be used to distribute heat in buildings and not just on circuit boards.

Before anyone asks, the article is clearly wrong in the statement "The new process causes the polymer to conduct heat very efficiently in just one direction...", the heat moves along one dimensions, in 2 directions.

"The new process causes the polymer to conduct heat very efficiently in just one direction,"

I was thinking, wow, is this even possible? If this is true, I think they've just created a material that could behave like a passive air-conditioner, heater, refridgerator, etc., while using NO power, ever. That alone must be breaking some serious laws of thermodynamics..

"One dimension" or "one axis," would have been more appropriate than "one direction."

"The new process causes the polymer to conduct heat very efficiently in just one direction,"

I was thinking, wow, is this even possible? If this is true, I think they've just created a material that could behave like a passive air-conditioner, heater, refridgerator, etc., while using NO power, ever. That alone must be breaking some serious laws of thermodynamics..

One dimension" or "one axis," would have been more appropriate than "one direction."

While this also seemed the most intriguing part of the post, it doesn't have to violate thermodynamic laws. A ratchet basically does this. So if you could create a ton of tiny ratchets out of polymers you could in theory create something that "conducts" heat in one direction. A diode conducts current in one direction......

That's a pretty intriguing idea too, but also in theory it is impossible to get energy out of that because the ratchet will actually slip due to its own thermal energy an average things out.. assuming a long period of time and all parts of ratchet being at thermal equilibrium. If the ratchet is at a lower thermal state then you really just have a miniature heat engine that extracts energy from the thermal difference, which becomes equalized. Source: http://en.m.wikipedia.org/wiki/Brownian_ratchet?wasRedi [wikipedia.org]

It wouldn't break any laws of thermodynamics. Say it only allows heat transfer from A to B.

If A is warmer than B, energy (heat) will flow from A to B (from warm to cold), decreasing A's temperature while increasing B's. This process decreases energy while increasing entropy, making it perfectly "legal" according to the laws of thermodynamics.

If B is warmer than A, nothing happens, or, perhaps more realistically, the heatsink now acts as a thermal insulator and only allows a very small amount of energy to go

No, no, no. Demons are chaotic evil, Devils are lawful evil, totally different things. DnD has taught me that much, at least. There's no indication that any of the demons in the band mentioned in that song were of the variety spoken of by Maxwell!

On the other hand, Maxwell's Demon brings order (law) to chaos. Maybe Maxwell misspoke and was talking about a devil?

I said this elsewhere but I'll say it here too:
Thermal bias != Maxwell's Demon.

The second law does not require that heat flow from hot to cold, only that there is a net increase in heat. Obviously this requires an external energy source, though.
And the water example is not a thermal bias, no, but it is a neat case. The water actually DOES transmit heat through a vertical column much faster in an upward direction via convection, than cooling (which is only aided by convection under 4C, which is an infl

Actually I have to change my stance. There has been a good argument made in this thread that a "thermal diode" wouldn't violate thermodynamics any more than an ideal insulator would (and we assume ideal insulators in models all the time without creating perpetual motion machines).

The real violation is when you have two regions of equal temperature, and you move heat from one to the other without spending more energy than what you're moving, creating a heat differential out of nothing and decreasing entropy

Very happy to see that this was immediately corrected by this AC comment. Thermodynamics does not allow for heat conductivity in just one direction. If such a material was possible it'll be simple to arrange it in such a manner that entropy spontaneously decreases e.g. having heat conducted one way towards a water reservoir. This accumulated thermal energy could than for instance be used to power a sterling engine making this a second class Perpetuum mobile [wikipedia.org].

Just for argument's sake, the jury is still out on 'thermal rectification'. The key is just that you can't ignore certain parts of entropy generation that will exist in such a device. Here's an abstract link from a young professor at UC-Riverside, currently getting a DARPA Young Investigator Award.

How would this be any different than the little spiny things in the light bulb with one dark side and one shinny/white side using heat difference to spin. You're not generating perpetual motion, you'd be using energy from the environment, it'd just resemble perpetual motion in that you'd wouldn't directly see the energy you'd just see a cold spot and a hot spot.

That said, i don't believe it to be possible, but not on any laws i know.

The little spiny thingy is a perfectly "normal" heat engine in that it exploits a thermal heat difference that is created by an influx of energy from an external source i.e. the photons that heat up the dark side.

The difference with a ideal uni-directional heat conductor is that it allows to create the heat imbalance out of thin air i.e. without putting in additional energy the entropy of the system is lowered. The wikipedia article that I linked to explains this in a bit more detail:

Having a material direct heat in 1 direction doesn't necessarily result in a perpetuum mobile. If said material only conducts heat from point 1 to point 2 if t1 > t2, and doesn't direct any heat in any direction if t1 t2, then it wouldn't break any law of thermodynamics.

It's not wrong, it's just using a more technical definition of "direction" than the one you're used to. In the mathematics and physics I was taught, a vector has three attributes: a magnitude, which is a positive number; a direction, which is similar to a line, not a ray (eg north-south, not just north; the x axis, not just positive x; etc.); and a third thing which determines which way it's going along that direction (a single bit, basically); I'm not sure what this last thing is called in English, so let'

Speaking of both being correct, the notion of a vector's direction can be considered both in the context of the line the vector follows combined with its sign, or separate.

For example if you define your vector in terms of 2d polar coordinates, Theta is your direction, and the magnitude could be positive or negative. It's just usually we define the direction of a vector such that its magnitude is positive.

You can also obviously refer to the sign-independent sense of direction as the dimension since you can

That’s true; positive/negative movement in one direction would equal forward/backward movement along one axis. However, in some cases, it makes no sense to speak of negative movement, and this is definitely one of those cases. Heat never moves backward: it always moves from hot regions to colder ones. So the assumption that the movement is always positive is a sensible assumption, and saying that the material only allows heat to pass in one direction is clearly the wrong way to describe what it does.

I will certainly agree that while the phrasing in the summary is correct if interpreted a certain (valid) way, it was a poor choice of words because it gives the wrong impression when interpreted the way that most people, even the scientifically minded, would take it in context.

Also, I think it's quite possible that whoever wrote that copy was not aware of the nuances we're discussing, and that "direction" in the sense they meant it is the one where the statement is simply wrong.:)

Before anyone asks, the article is clearly wrong in the statement "The new process causes the polymer to conduct heat very efficiently in just one direction...", the heat moves along one dimensions, in 2 directions.

Right, the article isn't talking about a
heat diode [technologyreview.com].

That is linear movement along one axis / in one dimension. It is not a direction. “Direction” is the way you are headed. You may be able to go forward or backward along that line, but forward and backward are always distinct.

If your direction is north, you’re situated along the north/south axis, but if you have a positive velocity then you’re moving toward the north. If your direction is south, you’re on the same axis, but positive velocity indicates that you’re moving to

The new process causes the polymer to conduct heat very efficiently in just one direction, unlike metals, which conduct equally well in all directions.

I think they mean in one dimension, not direction. The plastic will conduct heat longitudinally a lot better than laterally, but it will conduct heat longitudinally equally well both to and fro. If they ever come up with a material that only conducts heat in one direction (a thermal "diode", if you will) then that solves our energy woes.

If all polymer molecule strings are all oriented the same, is it a crystal?This setup may show interesting optical properties as well. It's amazing research really, with processing matter at that atomic scale control. Being able to buildup matter that precisely will reveal all new dreamed uses. I really hope this will go forward as discovering industrial processes of controlling matter buildup arrangement at an atomic scale in mass-production.

Since there's at least some variability, it might be best to characterize it as having a "high degree of crystallinity." Polyethylene oriented in this way sounds a lot like the ultra-high molecular weight polyethylene fibers marketed as Spectra and Dyneema. Those are made by an extrusion process called gel spinning, and the polymer chains also have a high degree of crystallinity and parallel order. I don't know if the oriented nature of gel-spun UHMWPE fibers is quite at the same level and provides the s

I don't know if the oriented nature of gel-spun UHMWPE fibers is quite at the same level and provides the same thermal properties as ones made by drawing them out with an AFM cantilever, but they might be "good enough," considering that gel spinning is a scalable industrial production method while cantilever drawing is a "very careful scientist" sort of method.

Well, I have a solution for that. Swap out all the CAPTCHAs on major sites for a webcam peering into an electron microscope that allows a person to draw out the polymer molecules with the cantilever. A week or two, tops, and you'll have someone who's created a bot that can do it perfectly.

Another, similar way is to have Blizzard do the same thing, except using it as a substitute for a CAPTCHA, for every molecule they pull, they get 1 silver piece added to an account of their choice. You'll get the same results, except the bot will speak Chinese.

Straight from Wikipedia, “A crystal or crystalline solid is a solid material, whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions.”

Aligning the polymer molecules in one dimension is not enough. They would have to be aligned in all three dimensions.

Since neither the summary nor the article has been kind enough to expand on "300 times more thermally conductive than normal polyethylene", I figured I'd look it up.Thermal Conductivity of some common Materials: [engineeringtoolbox.com]Polyethylene HD: 0.42 - 0.51 W/mKAluminium: 250W/mKCopper: 401 W/mK

Best case scenario: 153 W/mK or 61% as conductive as aluminium, 38% as conductive as copper. Not exactly impressive for a heat sink

Even if 61% of aluminum axed conductivity would have some uses, a heat sink need to have good interfaces with the heat source and with air or other transfer medium. this heat sink example is really inaccurate. Considering if expectations are for moving heat from one place to another, with limited scatter dissipation, the most efficient method is by having a mechanically moving medium (liquid coolant).

The problem with that is that most likely, the interface for the Polyethylene heat sink would be worse than for an aluminum one; The Polyethylene molecule is vastly more complicated than the Aluminum atom, and not nearly as mobile once cast (and would be just as likely to capture little insulating pockets of air, etc.). Even if the Polyethylene molecules on the end could "mold" to the interface, there is not guarantee they wouldn't flop over and become insulating - an Aluminum sink "molded" to the interface wouldn't care, as it's isothermal.

Actually, the interface between $HOT_SURFACE and $HEAT_SINK is usually coated w/ some sort of thermal grease to mitigate interface insulating effects. That little tube of goop that you use w/ your brand new ThermalTake heat sink fills micro voids w/ thermally conductive goo for both the processor and heat sink interface surfaces. Typically, a metal-to-metal interface is still mostly voids because you can only polish them so flat and smooth before you're using semiconductor grade (and cost!) processes and

So, you're getting a factor of 2-10x in weight savings. Tell that to a aerospace designer and he'll make it work. It's also a cheap material (well, feedstock's cheap. and normal PE is cheap, especially relative to copper these days). Who knows how expensive this stuff might be if they can make more than single fibers.

The number that gets dropped in the abstract [nature.com] is 104 W/mK. The highly oriented polyethylene fiber Dyneema has a listed thermal conductivity of 20 W/mK [matbase.com], so this figure would represent a significant advance from the polyethylene fibers currently out there. As you can also see, the "service temperature" for Dyneema tops out at 100C and it melts at about 150C. This new PE fiber with a higher degree of crystallinity would likely bump those numbers up slightly, but it would still be unsuitable for very high temp

This material could be another boom material for the spacecraft industry. Some of the heavier hardware on any given space payload is the thermal control system. Using a combination of heat pipes [wikipedia.org] and surfaces coated in various colors of paint for heat control can add a significant amount of weight to a spacecraft. If this material can be added as a thermal layer to the MLI [wikipedia.org] layers that are tacked onto the outside of a spacecraft, it may go a long way in reducing and simplifying the thermal control subsystem of the given payload. In fact, since it is a simple plastic, it should be significantly lighter than various metal contacts and conduction paths within a spacecraft that are used today.

The single dimension (not direction) transfer mechanism could also be very useful. If you can ensure that heat will move along only a single axis, you have a bit more freedom in placing sensitive components in and around your conduction paths within your spacecraft. All in all, this could be a really useful material, if it can ever be scaled up for use in industrial applications. Here's hoping.

Of course after being exposed to heat for a couple minutes the material transforms back into a chaotic tangled mass since the polymer molecules are only lined up the same way when at a lower temperature with less molecular volatility.

This fiber was about 300 times more thermally conductive than normal polyethylene

Since I couldn't find in TFA the ACTUAL measured conductivity, I turned to the internets:

Using data from the first source I found [engineeringtoolbox.com], at its highest, HDPE's thermal conductivity is 0.51 W/mK. So this material's thermal conductivity in that dimension is about 153 W/mK, or about 3/5 that of Al (250 W/mK), 3/8 that of Cu (401 W/mK), and between 1/6 and 1/15 that of diamond (900–2,320 W/mK, according to wikipedia [wikipedia.org].

So all in all, while this is very fascinating research (and I enthusiastically encourage them t

A very apt comparison since I only use diamond heat sinks for my gaming machines.

Diamond is widely considered to be one of if not the most thermally conductive material available. This comparison was included because for those familiar, it is a handy reference. It was as if, because your arms are too short to touch the ceiling, you believe it doesn't matter how high it is.

On a side note, there actually IS diamond thermal paste available for sale [innovationcooling.com]! Huzzah.

The ability to direct the heat flow can make up for a somewhat lower conductivity for many applications, and can also allow for layouts and applications which wouldn't work with metal heat sinks.

Since the primary issue with metal heat sinks is generally getting the heat wicked off of them, I'd be more apt to consider Finite E

Lovely, another case of life imitates sci-fi. This development reminds me a bit of the superconductors in some of Larry Niven's books (esp. the Ringworld series). In addition to being an electrical superconductor this material was also a thermal superconductor -- and was used as a sort of sci-fi super heatsink on a few occasions. It was mostly represented by ultra-strong threads, and occasionally a woven cloth IIRC.

And, this is where this material really would really fit into the Ringworld canon, <spoiler> the puppeteers toppled the Ringworld civilisation ([d]evolved humanesque Pak which seems scarily advanced to them) by introducing a "superconductor plague", i.e. some microscopic lifeform that ate this superconductor. Seems actually possible now with such an organic material which could probably be anaerobically metabolised.</spoiler>

Right, but the key part of the article was heat and stretch. There are other ways that this can be done to a plastic. Ever see fresh noodles be made by hand, by a master noodle chef?

The chef starts with a large amount of dough, and draws it out, "bouncing" it on the work surface covered with flour. He/she then folds and twists it upon itself and repeats the process many times: 1 very thick noodle, 2 thick noodles, 4, 8, 16, 32... you get the idea. 10 folds and twists give 1024 noodles (often it's folded upo

I'm not too clear on the manufacturing details here. But the material itself sounds a lot like the original Polaroid film (not the photographic kind, the polarizing kind), which is a type of plastic polymer, impregnated with iodine, which has been stretched in one dimension to align the polymer molecules along that dimension. The iodine atoms are able to conduct electrons between themselves, effectively forming "wires" which absorb radiation polarized along the direction of the molecules. I wonder if a bloc

"let loose the dogs of war" can be reworded to "to let the dogs of war loose"
Either way, both "let" and "loose" are verbs here.

"To let loose" is the unconjugated verb. Regardless of how you order the words, the verb (and there is only on in that phrase) is "to let loose". This is an example of a compound verb, which, in most cases, is a combination of two other verbs. It's important to note that when a compound verb is used, you cannot consider the verbs to be independent, as additional meaning is given